Purpose: The aim of the present study was to evaluate marginal bone loss (mBL) adjacent to dental implants with a machined surface with at least 5 years of function. Materials and Methods: Machined-surface implants with a minimum follow-up of 5 years were included in the study. Recorded clinical parameters included plaque and gingival bleeding indices, smoking habit (nonsmoker, 0 to 10 cigarettes/day, or more than 10 cigarettes/ day), presence of periodontal disease (healthy or periodontally compromised), and compliance with periodontal maintenance. Marginal bone loss (mBL) was assessed radiographically around the implants using the long-cone parallel technique. Results: Sixty-eight participants who received 217 implants were included in the study. No late failures occurred. The mean duration of follow-up was 6.7 years (range, 5 to 9 years). The mean mBL after 5 to 9 years was 0.43 threads (± 1.12 threads) (0.26 mm). Thirteen implants (6.0%) showed a mBL of at least three threads. Multiple linear regression (R2 = 0.229) showed that implants in patients with poor periodontal maintenance and implants placed in periodontally compromised patients were significantly associated with greater mBL (P .005). Female gender and follow-up time were also associated with greater mBL. Conclusions: Limited long-term mBL was associated with machined-surface implants. Regular periodontal maintenance visits every 3 to 6 months, especially in periodontally compromised patients, have to be considered paramount to maintain peri-implant bone levels over the long term. Schlagwörter: alveolar bone level, dental implants, periodontal maintenance, Plaque Index, risk factors, smoking